Traditional coating materials comprising latex polymer and coal ash are generally “two component” systems with the polymer in the form of a liquid dispersion (emulsion) and the coal ash as a powdered solid. Traditional “two component” coating material systems involving a liquid latex polymer and other solid material(s) require additional steps for preparation on a job site when compared with one component, dry mix systems. Two component systems typically require additional weighing or metering processes for “slurry” preparation when compared with one component, dry mix systems. Each additional weighing or metering step associated with two or more component coating systems introduces additional possibilities for error with each additional weighing or metering device when compared with pre-manufactured or pre-blended one component, dry mix systems. In addition to increased probability of error associated with field application of two or more component coating systems, latex polymers in liquid form are often susceptible to freeze damage. Typical behavior is that the polymeric dispersion will experience a morphology change upon freezing and thawing rendering the material no longer usable for coating applications. One component, dry mix systems are not susceptible to freeze damage and can be left on a job site in temperatures below the freezing point of water without being damaged. These two attributes provide motivation to replace traditional “two component” systems with one component, “dry mix” systems in the construction industry.
As a result of stricter guidelines for gaseous emissions, traditional coal fired power plants are either modifying their processes or adopting new technologies. Such process modification often influences properties of coal ash waste streams, making future production of fly ash with significantly higher carbon contents seem imminent. In addition to production of higher carbon content coal ash, these newly implemented technologies may also yield coal ashes which are not high in carbon content in terms of loss on ignition (LOI), yet these coal ashes will differ significantly from what has been regarded as the customary coal ash as lower process temperatures cause a morphology change from fused, spherical particles to platy type particles which are not completely fused. Nevertheless, whether a coal ash is high in carbon or not completely fused, such a coal ash is deemed “problematic” with respect to beneficial use within the cementitious materials industry.
In past regulatory environments, markets existed for fly ashes containing high contents of carbon—for example, coal ashes with loss on ignition (LOI) greater than three percent. During these times, one routine outlet for high carbon content fly ash was its use as feedstock to cement kilns. Various fly ashes may be high in silica and alumina containing compounds making these materials valuable contributors to cement production from a technologic point of view. Although fly ash may accordingly serve as a useful raw material for cement production, new industrial emissions standards may endanger such a promising outlet for fly ash. This is because fly ashes may also contain nuisance materials such as, for example, arsenic, mercury, lead, cadmium and zinc. When introduced to the high operating temperatures of a cement kiln, these materials have a tendency to transition into their respective vapor phases, thus becoming gaseous emissions. New emissions standards may force cement producers to seek raw materials that will not be significant contributors to unwanted gaseous pollutants. For this reason, fly ashes once used in cement kilns may be expected to end up in landfills. It is now becoming apparent that new regulatory regimes create new challenges for both the coal fired utilities industry and the cement industry. New regulations may clean up the air, but these regulations are continuing to pressure the industry with regard to finding outlets for waste streams.